Horizontal outdoor luminaires are well-known in the art. Such luminaires traditionally are made of cast aluminum construction and therefore have considerable weight. In addition, where such luminaires employ high intensity light sources, transformer or ballast and other power pad or power control components must be mounted within the respective luminaires. The power components such as ballast transformer are heavy in weight requiring such safety devices as that shown by U.S. Pat. No. 3,761,781 to J. R. Dean issued Sept. 25, 1973.
Typically horizontal luminaires for roadway lighting extend 25-40 inches from their mounting on the horizontal mast, and the luminaires fully assembled may weight in the range of thirty to sixty pounds.
In some of these luminaires, the power components are mounted on a pivotal door (U.S. Pat. No. 3,398,291 issued Aug. 20, 1968 and U.S. Pat. No. 3,353,015 issued Nov. 14, 1967).
Specifications for luminaires of this type require that the luminaire have an effective life of fifteen years under the normal operating conditions to which it is exposed in use.
With the development of engineering grade plastics or high impact plastics especially such plastics as glass filled polycarbonates, polyesters and nylons, the question has been raised as to why these plastics could not be used to replace the cast aluminum housings for luminaires. However, such plastics are known to creep in tension especially when subjected to temperature extremes and continuous vibration and therefore can not meet the operating specifications for the luminaires. In attempts to develop a plastic housing, suitable for a luminaire, many problems arose due to the drooping or creeping of the luminaires relative to its slipfitter mount, as a result of the weight of the power components, within the wide temperature ranges and vibrational forces to which the luminaire was exposed.